1. Technical Field
The present invention relates to inflation equipment for inflatable devices, and particularly to inflation valves as used thereon. More particularly, the present invention is an improved inflation valve of a puncture disc or "cutter" design for use with inflatable devices such as life rafts and escape slides. Specifically, the present invention is an improved inflation valve of a one-piece valve body design utilizing a puncture disc "cartridge" in conjunction with a livestock or hypodermic needle that is used as a bayonet for puncturing the disc whereby the valve is constructed in this "one piece" design for enhanced reliability and lower production and assembly costs.
2. Background Information
Inflatable life rafts have found wide use on ocean-going ships and aircraft as emergency flotation devices. An inflatable life raft offers the advantage of being light weight and of a small deflated size thereby providing an optimal safety device on ships and aircraft where space and weight are important considerations. Specifically, the deflated and packed life raft is stored in its deflated and packed condition for long periods of time when it is not needed, yet it can be inflated rapidly when it is needed to form a raft capable of holding people.
Inflatable life rafts are inflated using a pressurized inflation gas (such as carbon dioxide, dry air, or nitrogen) which is contained in a pressure tank or pressure vessel that is typically folded within the folded raft. When the raft is to be inflated, a valve is actuated by pulling a pull cable. The pull cable is connected at one end to the valve actuating mechanism in such a manner as to allow the cable to pull free after the firing mechanism has been actuated. When the pull cable is pulled, the actuating mechanism fires the valve causing it to open thereby permitting the pressurized fluid to expand and fill the life raft.
Of all of the various valve designs that have been used since life rafts were invented in the early 1940's, "puncture disc" design units have proven to be the most field reliable. This valve design uses a thin metal disc (the "puncture disc") which normally blocks the passage connecting the inlet of the valve (attached to the pressure tank) to the outlet of the valve (attached to the deflated raft). A bayonet or spear is provided for contacting and piercing an opening in the disc. An actuation mechanism is provided for moving the bayonet toward a collision with the disc that is sufficiently forceful to pierce or puncture open the disc. Gas then flows from the pressure tank through the inlet, through the passage, and through and/or around the hollow bayonet positioned in the rupture in the puncture disc to the outlet and then to the inflatable article, such as a life raft.
Puncture discs of various kinds have been proposed in the past. Examples of puncture disc inflation valves are shown in the following U.S. patents. Hinchman U.S. Pat. No. 2,120,248; Davis U.S. Pat. No. 3,266,668; Bernhardt et al. U.S. Pat. No. 3,526,339; Martin U.S. Pat. No. 3,757,371; McDaniel et al. U.S. Pat. No. 3,887,108; Milgram U.S. Pat. No. 3,938,704; Legris U.S. Pat. No. 4,356,936; and Mackal U.S. Pat. No. 4,475,664.
Prior art puncture disc valves were bulky and therefore often difficult to package. In addition, these prior art puncture disc valves are often hard or very inconvenient to charge or fill because of the difficulty of bypassing the sealing disc without damaging or contaminating the disc seal.
In response to industry requests for improved field reliability, Mirada Research & Manufacturing designed and patented a two part Improved Raft Inflation Valve as disclosed in U.S. Pat. No. 4,959,034. In general, this valve included a cutting head disposed on a bayonet piston for cleanly puncturing a puncture disc. This valve was designed and constructed with a two part valve body. Specifically, the valve body is a cylinder head and a firing head. This and other prior art designs all incorporate two or more piece valve bodies which have provided the necessary interior access to the disc cavity but which are expensive to manufacture.
In addition to expense, the puncture disc inflation valves with multiple part valve bodies are susceptible to poor assembly or inaccurate part insertion. Specifically, as to the '034 inflation valve, it has been found that in the rare case of a valve failure, such failure is almost, if not always, attributed to either poor assembly or re-assembly of the two part valve body or insertion of too many puncture discs (that is, more than one).
This '034 valve has become a very popular valve in the inflation valve industry. The field performance and reliability of the '034 valve is highly acclaimed in the inflatable industry where the '034 valve (and other puncture disc type inflation valves) continue to routinely outperform all other non-puncture disc design inflation valve types. In addition, although the '034 puncture disc valves provide user friendliness and ease of repair unmatched by its non-puncture disc counterparts, these valves do require proper assembly and assurance of the correct number of discs for proper and reliable field performance.
In addition, although puncture disc valves provide superior performance over non-puncture disc valves, some raft builders still use non-puncture disc valves for several reasons. These reasons are primarily cost, weight, and specific design constraints, configurations and limitations. Therefore, a new design of a puncture disc valve is needed to satisfy these concerns of the raft builders not using puncture disc valves as well as the other listed disadvantages and concerns as to current puncture disc designs.